I do not like the RAW conversions that Aperture is making from my 20D. They are not as nice as ACR, and the tools are not as easy to use. Currently Aperture is only good for the capture / selection / database side of things and NOT raw conversion.
I was using iPhoto for capture / database etc. of photos, and it worked fine, but was slow. Aperture is a lot quicker at this, and nicer.
I've made some folder actions to auto-import an exported RAW from Aperture into Photoshop, and to take the finished PSD back into Aperture. It works, but is a hack.
Apple need to decide what Aperture is - is it capture / catalogueing, or is it RAW conversion/image adjustment.
Unless they can meet Adobe ACR quality for RAW conversion, they're dead in the water as far as that's concerned as you just loose picture quality using Aperture, and that's not good. If it's the capture/database side of things Apple are aiming at, then they need to address Photoshop PSD workflow to make it a lot smoother, and to handle a lot more of the types of images Photoshop does, like LAB files etc.
Apple can't expect photographers to do "everything" in Aperture, if they don't meed established image processing standards. Until then, I'm happy enough using it as a databse, but Aperture should be a lot lot better than it is.